82 urasteri;e. 



is the species of Linnaeus, as may be seen by consulting the 

 characteristic figures of Link to which he refers. Asterias 

 tenuispina of Lamarck is, I doubt not, a variety of this, 

 with more rays than usual. The Asterias Saveresi of 

 Delia Chiagi is also a variety ; and that author does 

 wrong to unite Asterias violacea of Muller with the Uraster 

 glacialis. 



Its rarity is probably owing to its habitat, rocky places 

 in deep water. The Hebridean locality is an exception ; 

 but it is a remarkable fact, one which I have elsewhere 

 pressed on the attention of geologists when considering the 

 Mollusca, that whenever, as in the Hebrides, the tides fall 

 but a few feet, these animals, usually inhabitants of deep 

 water, may be found living above low water mark. This 

 holds good as well in regard to Radiata as to Mollusca ; 

 and the mixture of species generally considered inhabitants 

 of the depths of the sea, with truly littoral species, should 

 a fossil bed be formed, might lead to false conclusions 

 unless such fact be borne in mind. Thus a change in the 

 tides of a line of coast would materially affect its fauna. 



